Fluid Pressure Research Articles

Targeting extracellular matrix stiffness for cancer therapy

The physical characteristics of the tumor microenvironment (TME) include solid stress, interstitial fluid pressure, tissue stiffness and microarchitecture. Among them, abnormal changes in tissue stiffness hinder drug delivery, inhibit infiltration of immune killer cells to the tumor site, and contribute to tumor resistance to immunotherapy. Therefore, targeting tissue stiffness to increase the infiltration of drugs and immune cells can offer a powerful support and opportunities to improve the immunotherapy efficacy in solid tumors. In this review, we discuss the mechanical properties of tumors, the impact of a stiff TME on tumor cells and immune cells, and the strategies to modulate tumor mechanics.

More accurate representation of interaction at the fluid–structure interface with an improved smoothed field gradient method

Flexible structures are wind-sensitive with a significant fluid–structure interaction (FSI). The FSI analysis, however, often has poor numerical stability and low convergence efficiency due to drastic changes of the physical fields induced by computation errors in local regions of the fluid–structure interface. This paper aims at addressing these problems with the proposal of a new method to smooth the gradient of the pressure field at the fluid–structure interface for an efficient convergence in the FSI analysis. The smoothed gradient theory is modified by introducing weight coefficients. The field of fluid pressure in each smoothing domain with large numerical fluctuations at the interface is then gradient smoothed with the proposed method and the modified field is obtained from the linear Taylor series expansion. The convergence of fluid and structure solvers for the proposed method is ensured within the commercial software FLUENT and ANSYS adopted. The proposed method is validated with experimental results from the literature. It is also numerically validated with a thin plate in viscous flow with different site categories and average wind velocities through comparison of results from conventional methods. The proposed method is found valid and accurate in the FSI analysis. It is relatively independent of a wide range of parameters with satisfactory robustness and notable improvement in the convergence of the FSI analysis.

HYDROSTATIC TESTING TECHNOLOGIES IN THE METALLURGICAL INDUSTRY

The development of the new test presses is based on the requirements of modern technologies for the extraction of oil from ultra-deep wells and shale gas to test the strength of pipes up to higher test pressures. The hydrostatic test algorithm involves pushing test heads onto the ends of the pipe to seal the internal cavity of the pipe. Then the pipe is filled with a water emulsion and the pressure of this emulsion is increased to the value specified in regulatory documents. For high-pressure hydrostatic testing of oil and gas pipes, the most advantageous method is the external sealing of pipes using segmental sleeves. The mechanical testing equipment should take into account the compensation of axial forces from the pressure of the test fluid inside the pipe, for which purpose the press frame should be power-operated. The most common power scheme of test presses is considered, in which all axial forces arising from the action of the fluid pressure inside the pipe on the test heads are compensated by reaction forces in the power columns. The front head is rigidly connected to the columns, and the rear head is placed on a movable carriage to compensate for uneven pipe lengths. In the working position, the rear carriage is fixed to the columns with special locking mechanisms. It is advisable to improve the quality of the test by improving the design of the hydraulic system elements and studying the processes during the rise and retention of high pressure. The test pressure inside the pipe is created mainly by means of a hydraulic pressure multiplier. The parameters of the multiplier: multiplication factor, piston diameter and stroke are selected depending on the required test pressure, length and diameters of the pipes to be tested. Research on high-pressure hydraulic systems of the multiplier type is of particular interest at present.

Design and experimental study of a new hydraulic tool for lost-circulation materials (LCM) plugging while drilling

Big Data Analysis from the worldwide field shows that lost circulation is a common phenomenon in drilling and the success ratio of remedial treatment for lost circulation is low. It is not only because of these complexities of the formation, but also because of the poor performances of the lost-circulation materials (LCM) and technologies. This paper proposes a new method in plugging, which is based on a particular physical method for lost circulation controlling and plugging while drilling. This method is different from these traditional treatments, which only use chemical methods. When pore-permeable and fractured leakage formations are encountered while drilling, We can use this new hydraulic tool, the drilling fluid will have a diffluence at a constant rate from the jet of the hydraulic tool which is installed on the drilling pipe and the fluid laden with particles can be injected into the natural or induced fractures of the borehole wall which may lead to lost circulation. Combined with the corresponding drilling fluids which have been tested in the laboratory, the additives such as ground marble, ground nutshells, and graphite in the drilling fluid are quickly pushed into the fractures because of the differential pressure provide by the hydraulic tool, then form a firm seal at the mouth of the fractures which could isolate fluid pressure in the wellbore and prevent effective pressure communication to interfere the extension of the fracture. What’s more, according to the stress cage theory, when these sealing particles which prop the fracture open, act as wedges to compress the rock around the wellbore, the hoop stress could be increased, so that the wellbore pressure containment (WPC) could be improved. Since the annular flow may have some interference with the side nozzle jet, this paper also numerically simulates the flow field of the annular air section through the fluid simulation software Fluent, and the simulation results show that the interference of the annular flow on the jet is very weak and basically has no effect. In addition, through the oilfield field test, it is known that this new physical plugging method has good plugging effect, and it can obviously improve the pressure-bearing capacity of the formation, which has great popularization value.

Propped fracture conductivity in shale oil reservoirs: Prediction model and influencing factors

Hydraulic fracturing is the main measure for stimulation of shale oil reservoirs, but the high content of clay minerals, well-developed bedding, and low mechanical strength of shale rock often result in a strong stress sensitivity of propped fractures associated with shale hydration expansion and proppant embedment in fracture wall. Especially under conditions of low sand laying concentration, the fracture conductivity can be greatly reduced. In this paper, a comprehensive prediction model of propped fracture conductivity in shale oil reservoirs was established, which considers the damage mechanisms of proppant compression, embedment, crushing, and shale hydration and expansion. The sensitivity analysis of factors affecting the fracture conductivity indicates that the proppant particle size, involved damage mechanisms, Kozeny-Carman coefficient, proppant layer number, and proppant density are the main factors to determine the fracture width and permeability and further affect the fracture conductivity. Most of the rest factors are related to the specific fracture damage mechanisms. The influence of shale hydration expansion is larger than that of proppant particle compression which is further larger than that of proppant crushing. In a real hydraulic fracture, the fracture width decreases from fracture heel to toe, caused by the non-uniform laying concentration of proppant. For the fracture near the wellbore usually with a large sand laying concentration, the influences of different factors are ranked as follows: proppant particle size > elastic modulus of proppant > fluid pressure > hydration expansion coefficient > filtration depth. For the front of the fracture with a low sand laying concentration, it is easy to close, which is sensitive to all the above factors. To achieve a high and stable fracture conductivity, the anti-swelling agent should be used to prevent shale hydration expansion. Large-size proppants with high elastic modulus should be selected to prop up the front of the fracture, and the decline of bottom-hole flow pressure should be controlled during the depressurized production process. The obtained results have a certain guiding significance for understanding the factors of shale fracture conductivity and the optimization of fracture parameters.

Mathematical modeling and CFD investigation of the novel oscillating shear valve generating sinusoidal signals by fluid pressure fluctuation

The oscillating shear valve pulser is a critical component of advanced downhole high-speed transmission systems, playing a vital role in efficient drilling operations. It is highly valued for its flexible and accurate source signal modulation capabilities, as well as its ability to operate safely without blockages. Specifically, how to ensure that the oscillatory shear valve pulse generator produces high-quality sinusoidal differential pressure source signals is particularly crucial. Consequently, this paper initially considers the motion characteristics of the shear valve in acceleration-uniform speed-deceleration, derives the calculation formula of the throttle area of the valve hole based on the fan-arc-fillet-line, and adopts the latest unsteady-liquid thin-walled cutting-edge throttling mechanism (UTCTM) we discovered, innovatively proposing the mechanism model of the differential pressure signal generation of the oscillatory shear valve. Based on this model, a typical optimized four-blade oscillatory shear valve was obtained. Through a series of CFD computational fluid dynamics studies, the amplitude variation characteristics and sinusoidal morphology evolution laws of the differential pressure signal at different frequencies were revealed, forming a unique design method for oscillatory shear valves, which provides a solid theoretical basis and technical support for the development of a new generation of pulsers.

A variationally-consistent hybrid equilibrium element formulation for linear poroelasticity

A poroelastic medium is defined as a continuous system in which the mechanical response arises from the interaction between a deformable elastic solid skeleton and a pressurised fluid, fully saturating the interconnected porous network. The coupled theory of Poromechanics is effectively employed to solve a broad class of problems spanning various fields, ranging from its original application in Geomechanics to addressing contemporary challenges in tissue Biomechanics. Besides the seminal theory introduced by Biot, several variational multi-field principles have been proposed, leading to various finite element formulations. Finite Element approaches are mostly based on a two-field discretisation involving the coupled solid displacement and interstitial fluid pressure as primary variables. However, this choice of the two-primary variables leads to a saddle-point problem, posing a challenge in achieving accurate solutions and thus making the use of stabilisation methods rather mandatory. This study proposes a novel variationally consistent Hybrid Equilibrium Element formulation, based on the complementary strain energy function. A two-field minimisation principle is formulated, with total Cauchy stress and interstitial fluid pressure serving as primary variables. The proposed variational principle provides a variationally consistent framework for designing inherently self-equilibrated Hybrid Equilibrium Elements, where the solid displacement field emerges as a Lagrangian variable to enforce a co-diffusivity constraint at element sides. The fulfilment of the inf-sup condition, typically challenging in developing stable and computationally efficient finite element formulations, is no longer required, a minimisation principle having been adopted, rather than the classical saddle-point principle. The proposed Hybrid Equilibrium Element approach offers a statically admissible solution even in the proximity of singularities or high space gradient stress distribution, providing a more comprehensive assessment of stress distributions and concentrations. The convexity of the new variational principle has been established, ensuring solution uniqueness. The formulation is based on a 2-D triangular Hybrid Equilibrium Element employed to solve plane strain problems. The element has been implemented in the Open source Finite Element Analysis Program (FEAP) and its performance evaluated against classical benchmark problems for poroelasticity, with the emphasis on stress accuracy. The numerical results obtained for the quasi-static analysis of poroelastic systems show the advantages of the proposed approach, in which accurate stress distributions are displayed, even adopting quite coarse meshes. Remarkably, in the proposed approach no stabilisation technique is required.

The role of fluids in earthquake swarms in northeastern Noto Peninsula, central Japan: insights from source mechanisms

AbstractA prolonged earthquake swarm has persisted since June 2018 in northeastern Noto Peninsula (central Japan), with activity focused into distinct southern, western, northern, and eastern clusters. To explore the role of fluids in the occurrence of this swarm, we analyzed the focal mechanisms of the earthquakes occurring from 1 January 2018 to 30 November 2022 and performed stress tensor inversions. The western, northern, and eastern clusters were dominated by a reverse fault-type mechanism with a horizontal P-axis oriented NW–SE. One of the nodal planes of those mechanisms aligns closely with the precisely relocated hypocenter distribution. The stress fields in these three clusters, as determined by stress tensor inversion, have maximum principal stresses oriented horizontally in the NW–SE direction and minimum principal stresses oriented vertically, aligning with the regional stress field. From these focal mechanisms and this stress field, we derived small misfit angles and large slip tendencies. These findings suggest that, in these three clusters, fluids diffused into faults largely aligned with the regional stress field, resulting in earthquakes with compatible focal mechanisms. Conversely, normal and strike-slip fault-type focal mechanisms, which are unfavorable to the regional stress field, dominated in the southern cluster. The estimated stress fields, deviating from the regional stress field, have maximum principal stresses closer to vertical and minimum principal stress oriented horizontally in the ENE–WSW direction. For earthquakes deeper than 15 km, this local stress field results in relatively larger misfit angles and lower slip tendency than the other clusters. These results suggest that those earthquakes in the southern cluster occurred on misoriented fault planes due to elevated pore fluid pressures. These findings provide strong evidence of the ascent of high-pore-pressure fluids from depth in the southern cluster and their subsequent diffusion into a southeast-dipping fault zone. Graphical Abstract

Causes and Evolution of High Injection–Production Ratios in Low-Permeability Reservoirs: The Role of Water Absorption in Barrier and Intercalated Layers

During the waterflood development of low-permeability reservoirs, the lithology of barrier and intercalated layers adjacent to the reservoir, with specific permeability and porosity, has a significant impact on water injection efficiency and reservoir energy recovery. However, current research on injection–production parameters and pressure changes in low-permeability reservoirs has not fully considered the effect of these barrier layers. Therefore, this study focuses on the Chaoyanggou Oilfield, a typical low-permeability reservoir, aiming to reveal the influence of water absorption by barrier layers on water injection efficiency and pressure changes in the reservoir. The study systematically analyzes the evolution of the injection–production ratio at different development stages by constructing a comprehensive lithological geological model and applying numerical simulation methods. It explores how the water absorption characteristics of barrier layers affect reservoir pressure and injection efficiency. The results demonstrate that argillaceous siltstone and silty mudstone have significant water absorption effects on injected water, critically influencing pressure distribution and fluid flow dynamics in the reservoir. As the water cut increases, the injection–production ratio gradually stabilizes, and the elastic water storage in the reservoir becomes crucial for establishing an effective oil displacement system. The water absorption of barrier layers accounts for 30% to 40% of the injected water. A high injection–production ratio alone does not lead to rapid energy recovery or increased production. Only by balancing the injection–production ratio, reservoir pressure, and water absorption in barrier layers can the efficiency and recovery rate of waterflood development in low-permeability reservoirs be further improved.

Localization and Delocalization During Seismic Slip

AbstractThe thickness of a seismic slip layer controls style and rate of rupture propagation, frictional heating, weakening, and energy budget of earthquakes. Slip layer thickness changes dynamically with feedbacks between temperature rise, roughness, damage, and fluid pressurization. Natural faults have complex slip histories, ambiguating which layer thicknesses represent a record of seismic slip. The thickness of proven paleoseismic slip layers in nature are 1 mm–1 cm. Thicker slip layers do not get hot enough to retain coseismic frictional temperature anomalies and thereby prevent the detection of big earthquakes using current methods. We suggest that delocalization—the spontaneous increase in slipping layer thickness during slip—plays a role in coseismic healing and cause biases in the rock record of earthquakes. Recognizing the importance of feedbacks affecting slipping layer thickness is critical to understanding strength and stress variations during earthquakes and to correctly interpreting earthquake source parameters from exhumed faults.

Effect of reaction rate and pore structure heterogeneity on reactive solute transport in porous media

CO2 geological storage is the most direct and reliable method to reduce CO2 emission, and deep saline aquifers have the greatest storage potential of CO2. In the process of CO2 storage in saline aquifers, mineral precipitation and dissolution caused by reactive solute transport have a significant impact on reservoir storage potential. In order to predict the transport characteristics and storage potential of CO2 in saline aquifers, it is critical to understand the relationship between chemical reactions and transport properties. The governing equations of porosity evolution of porous media considering chemical reaction processes are proposed, and the relationship between effective reaction area and porosity is considered, and finally a kinetic model is established. Considering different reaction rates and different pore structure heterogeneity, the evolution characteristics of porosity, species concentration and fluid pressure were obtained by combining advection-diffusion equation and Darcy's law. The simulation results show that the dimensionless porosity of porous media transforms from uniform variation to extreme non-uniform variation under low Da number, typical Da number and high Da number condition. The dimensionless concentration can not reach the saturation concentration under low Da number condition. The dimensionless concentration decreases significantly in the inlet region and reaches the saturation concentration under typical Da number condition. The dimensionless concentration reaches the saturation concentration rapidly in the inlet region under high Da number condition. The variation of dimensionless pressure gradient in porous media is significantly correlated with the porosity distribution. The dimensionless advection mass flux of porous media is negatively correlated with the pore structure heterogeneity, while the dimensionless diffusion mass flux is positively correlated with the pore structure heterogeneity. The specie peak concentration decreased with increasing heterogeneity, and the time to reach the peak concentration increased with increasing heterogeneity. The research results can provide a theoretical foundation for the assessment of the transport pathways of CO2 storage in saline aquifers.

Stable-to-dynamic expansion of fault slipping area through fluid injection observed in laboratory experiments using a sub-meter scale specimen

In the field, locally applied fluid pressure can initiate fault slip, which may expand unstably over a wide area under certain conditions, generating elastic waves and inducing earthquakes. Therefore, examining the unstable expansion of the initial slip is important. However, reproducing this process in laboratory experiments, such as triaxial loading tests on small cylindrical specimens with inclined faults, is challenging. To achieve this, we prepared a sub-meter-scale cubic specimen, which was separated into two triangular prisms by a model fault. The specimen was subjected to biaxial compression of different magnitudes. A 2D array of strain gauges was embedded beneath the fault plane to measure the changes in shear strain with fault slip driven by fluid injection. Based on the experimental results, we discussed the features of the injection-induced fault slips that lead to earthquakes. The strain increased locally around the edge of the fault slipping area by approximately 10 με, which is equivalent to a shear stress of ~ 0.1 MPa. The fault slipping area first expanded gradually and then unstably beyond the fluid invasion area approximately 3 s after the slip was initiated. The unstable expansion of initial slips was suppressed by reducing the initial shear stress on the fault by 0.3 MPa. In this case, the initial shear stress was possibly too small for additional stress to accumulate at the edge of the fault-slipping area to overcome the static frictional strength of the fault. Our experimental study explicitly confirms that injection-induced aseismic slip can outpace the fluid migration front, finally leading up to a runaway rupture. It also confirms that the level of initial shear stress is important in controlling the rupture size under fluid injection.Graphical

Fluid-mediated transition from dynamic rupturing to aseismic slip at the base of the seismogenic continental crust

Chemo-mechanical fluid-rock interactions are critical in controlling the frictional-viscous transition in the continental crust and the competition between seismic and aseismic deformation in fault zones. In this study, we provide quantitative constraints on the timing and magnitude of weakening, and associated changes in slip rates, due to fluid-rock interactions at the base of the seismogenic continental crust. Integrating field, microstructural analyses, and micromechanical modelling we constrain the microstructural and mechanical evolution of phyllosilicate-rich, carbonate-bearing brittle-ductile faults/shear zones developed in the Rieserferner granitoid pluton (Eastern Alps). Here, transient overpressure of (H2O + CO2)-rich fluids triggered dynamic rupturing in the strong host rock (>100 MPa), and promoted the development of weak phyllonites through long-term fluid-mediated feldspar-to-mica reactions. These phyllosilicate-rich fault rocks accommodated frictional-viscous aseismic creep at very low differential stresses (<10 MPa) and near-lithostatic fluid pressure conditions. Microscale vein networks overprinting the phyllonite indicate cyclical embrittlement related to increased creep rates (up to 10−7 s−1) that occurred over a timeframe of days to months and potentially related to slow earthquakes (slip rates of 10−8 m/s). These findings offer new constraints on the development and seismogenic potential of phyllosilicate-rich fault zones and on the effect of fluid chemistry on fault zone rheology. Fluid-mediated fault weakening can occur in rather short time (months-to-years) comparable to the interseismic period, progressively promoting long-term, viscous aseismic creep on a previously strong fault zone developed by dynamic rupturing. The combined effect of strain localization, the low permeability of the phyllonitic cores, as well as of fluid chemistry evolution and CO2-enrichment, may lead to the development of brittle-frictional instabilities during transient accelerated-creep events. Therefore, the fluid-mediated microstructural evolution of phyllosilicate-rich fault rocks controls their seismogenic behaviour, potentially leading to accelerated creep, slow earthquakes and slow slip on otherwise aseismically creeping faults.

A Comparative Analysis of Alpha and Beta Therapy in Prostate Cancer Using a 3D Image-Based Spatiotemporal Model.

In treating prostate cancer, distinguishing alpha and beta therapies is vital for efficient radiopharmaceutical delivery. Our study introduces a 3D image-based spatiotemporal computational model that utilizes MRI-derived images to evaluate the efficacy of 225Ac-PSMA and 177Lu-PSMA therapies. We examine the impact of tumor size, diffusion, interstitial fluid pressure (IFP), and interstitial fluid velocity (IFV) on the absorbed doses. An MRI-based geometric model of the tumor and its surrounding environment is initially developed. Subsequently, COMSOL Multiphysics software is utilized to solve convection-diffusion-reaction equations and conduct numerical analyses of blood pressure distribution. This computational methodology provides valuable insights into interstitial fluid patterns and the spatiotemporal distribution of extracellular and intracellular concentrations of 225Ac-PSMA and 177Lu-PSMA. In addition, our study investigates the impacts of increasing tumor size on absorbed doses and mechanisms involved in radiopharmaceutical transport and delivery. Larger tumors have diminished absorbed doses, highlighting the need for customized treatments according to tumor size. Diffusion significantly influences the transport and delivery of radiopharmaceuticals. Additionally, alpha therapy was observed to consistently yield higher absorbed doses within the tumor than beta therapy. This study reveals the complex interplay between radiopharmaceutical properties, the tumor microenvironment, and treatment outcomes. It highlights the potential of 225Ac-PSMA in prostate cancer treatment, advocating for personalized treatment strategies tailored to the specific characteristics of each patient and their tumor.

Statistical Shape Modeling to Determine Poromechanics of the Human Knee Joint.

Subject-specific knee joint models are widely used to predict joint contact mechanics for individuals but may not capture the variance in knee joint geometry across a population. Statistical shape modeling uses the dataset of a cohort to encapsulate population-wide variability. The present study aimed to develop a shape modeling procedure for poromechanical finite element models of knee joint to account for population diversity in the creep response of knees. Shape models of right knee joints were created from MRI of 31 healthy male subjects using principal component analysis. Creep analysis was performed for 13 shape models in total, i.e., the average model, plus six models for both the first and second principal modes. For a given loading, the contact and fluid pressures varied substantially within these mathematically produced models but compared reasonably well to that of three subject-specific models that were constructed from individual knees, representing approximately the smallest, median and largest knees of the 31 right knees. While the joint size variation, generally represented by the first principal component, predominantly influenced the magnitudes of contact and fluid pressures, the joint shape variation characterized by the second principal component further affected the pressure distribution, and load sharing between the lateral and medial compartments. The present study evaluated a workflow for the statistical shape modeling of poromechanical behavior of knee joints with sample results based on a small population. However, the workflow can be readily used for a large population to address the challenge of interpatient variability in joint contact mechanics, particularly in contact and fluid pressures in articular cartilage, and variable creep behaviors of the joint associated with individual anatomical variations.

A Multi-Scale Thermal-Mechanical Numerical Method for Mini-Channel Heat Exchanger Subjected to Fluid Pressure Loads

Abstract This study proposes a novel multi-scale numerical method for thermal-mechanical analysis of mini-channel heat exchangers (MCHEs) under internal fluid pressure and temperature loads. The method comprises a macro-scale model for global analysis and a meso-scale model for detailed submodel analysis, specifically focusing on the internal fluid pressure effects within the MCHEs. The macroscopic model divides the MCHE into cover plate and homogenized regions subjected to pressure and temperature loads. To incorporate internal pressures into the homogenized MCHE model, mathematical equations are formulated to convert internal fluid pressures into equivalent strain loads. Additionally, a novel equivalent thermal expansion method is introduced, integrating internal fluid pressure loads by prescribing equivalent thermal expansion coefficients alongside spatially-varying nodal temperature fields within the MCHE. The meso-scale models with detailed channel patterns are assigned to specific portions of the homogenized region. The integration of the mesoscale model into the macroscopic framework is achieved through the application of the submodel method. Comparisons between the equivalent and actual MCHE models show that the proposed equivalent method can provide accurate predictions for thermal-mechanical deformations and stresses, and significantly reduce the computational expenses.

Impact of knee geometry on joint contact mechanics after meniscectomy.

Finite element modeling has served as a cornerstone in understanding knee joint mechanics post-meniscectomy, yet the influence of varying knee geometries remains unknown. The present study aimed to fill that gap by employing statistical shape modeling to generate knee models from MRI data of 31 human knees, capturing the population's knee size and shape variations. Finite element simulations were conducted to replicate intact, partial, and total medial meniscectomy conditions during standing. The results revealed a substantial shift in load distribution from the medial to lateral compartment following medial meniscectomy with its magnitude depending on knee geometry. Cartilages experienced variable degrees of pressure changes at different sites, which could also be different for fluid and contact pressures. While changes in joint size led to somewhat predictable alterations in contact pressure, variations in joint shape resulted in unexpected changes in contact and fluid pressures, emphasizing the need for computational simulations. The average knee geometry exhibited the lowest contact and fluid pressures under the given loading and boundary conditions, in contrast to knees with shapes deviating from the average. This study highlights the significance of individual knee shape in the biomechanical outcome of meniscectomy, potentially explaining the variability in clinical outcomes observed post-surgery.

Shuntogram technique for diagnosing shunt failure in patients with programmable valves: A literature review and a case scenario

Diagnosing shunt patency is crucial in the neurosurgical care of patients with shunted hydrocephalus. The shuntogram is a commonly used method to assess patency, yet its utility in accurately diagnosing shunt failure remains inconsistent. In this article, we examined studies on shuntograms performed in patients with fixed-pressure valves to clarify the techniques used and establish criteria for interpretation. We further reviewed conflicting evidence in the literature regarding the utility of shuntograms and outlined our institution&amp;rsquo;s protocol in the context of programmable valves. Studies included in this review detailed the following elements of shuntogram techniques: patient age, indication for shunt failure assessment, positioning, skin preparation, imaging protocol, contrast agents, patency testing, criteria for negative and positive results, troubleshooting shunt, and sensitivity and specificity of findings. Selection criteria included vague symptoms of shunt malfunction in the presence of non-diagnostic imaging. Patients were typically positioned supine or recumbent, with skin prepared using iodine-based products. Shunts were accessed using a 23 &amp;ndash; 25-gauge needle, observing cerebrospinal fluid pressure and aspirate. The contrast agent most frequently used was 99mTc-diethylene-triamine-pentaacetate, although the exact volume injected was inconsistently reported. Imaging protocols were not standardized, with delayed imaging intervals usually ranging from 9 to 20 min. Failure criteria for shuntograms varied significantly, with limited guidance on follow-up interventions or troubleshooting. Notably, there was no mention of shunt reprogramming during these studies. This review highlights the significant variability in shuntogram techniques and outcomes. We present our institution&amp;rsquo;s protocol and a case scenario demonstrating successful implementation. With proper techniques and protocolization, shuntograms hold the potential as a valuable resource for accurately diagnosing shunt patency.

A general Physics-Informed Neural Network approach for deriving fluid flow fields from temperature distribution

One attractive application of Physics-Informed Neural Network (PINN) is deriving fluid flow information such as velocity and pressure from temperature field. However, this requires developing a suitable loss function for a given flow condition. In this paper we implemented a general loss function in PINN to directly obtain fluid velocity and pressure from temperature information. We first validated this method through cases of natural convection in a square cavity, flow around a cylinder in a square cavity, and two-dimensional channel flow. Additionally, we examined forced convection heat transfer around a cylinder in depth. Results show that different Reynolds numbers (2, 10, 40, and 140) can all be effectively resolved using temperature data. Furthermore, super-resolution predictions of temperature, velocity and pressure are achievable even far outside the training area, suggesting that the proposed PINN method could be used to measure fluid flow within confined spaces via finite visualization windows without tracers.

Effect of cutting fluid supply conditions on tool loads during continuous and interrupted orthogonal cutting

AbstractIn metalworking, cutting fluids play an important role by reducing heat and friction during machining, extending tool life, and improving surface finish. Although the positive effects of cutting fluid have been confirmed in many studies, the relevant cutting fluid parameters such as nozzle cross-section area and supply pressure, as well as their influence on the thermo-mechanical loads of the cutting tool, have been insufficiently investigated. This study investigates the effects of cutting fluid supply conditions on tool loads during continuous and interrupted orthogonal cutting processes. The research specifically addresses the impact of nozzle geometry and fluid jet orientation on the thermo-mechanical loads on the cutting tool, which have been underexplored in previous studies. A prototype tool holder, designed and additively manufactured for this purpose, allows for variations in nozzle geometry and jet orientation. Experiments were conducted under varying cutting parameters, nozzle geometries, and fluid pressures, with tool temperature being monitored through an embedded thermocouple. The results show that nozzle geometry significantly affects chip shape, which directly affects cooling efficiency and, consequently, tool temperature. The study also uses an inversely calibrated analytical model to analyze the tool temperature distribution, which shows that the highest temperatures occur in the tool-chip contact area, while temperatures outside this area decrease rapidly. In addition, the percentage of heat conducted into the tool decreases with increasing Péclet number, which is consistent in both continuous and interrupted cutting scenarios. These findings provide a deeper understanding of how cutting fluid nozzle design affects tool performance and establish a foundation for model-based temperature analysis in machining processes.